Optoelectronic transceiver for a bidirectional optical signal transmission

ABSTRACT

An optoelectronic transceiver for a bidirectional optical signal transmission including a housing having a width of at most 13.5 mm, a first bidirectional optical subassembly arranged in the housing and serving for the simultaneous emission and reception of optical signals, a second bidirectional optical subassembly arranged in the housing and serving for the simultaneous emission and reception of optical signals, and an optical interface for the coupling of two optical waveguides, it being possible for a respective optical waveguide to be optically coupled to a subassembly. The invention enables a simultaneous bidirectional data transmission on both ports of the transceiver and thus an increase in the transmission capacity of the transceiver.

FIELD OF THE INVENTION

The invention relates to an optoelectronic transceiver for abidirectional optical signal transmission.

BACKGROUND OF THE INVENTION

What are known as industry standard are so-called small form factor(SFF) transceivers and small form factor pluggable (SFP) transceivers ofsmall design which are arranged in a housing. In this case, thetransceivers may be of pluggable design (SFP transceivers) or be fixedlyconnected to a housing (SFF transceivers). The known transceivers have,in addition to an optoelectronic transmission module and anoptoelectronic reception module, an internal printed circuit board whichruns parallel to the optical axis of the transceiver and containselectronic circuits for the converter modules, such as a driver moduleand/or a preamplifier module. The transceiver is arranged on a maincircuit board, which is electrically connected to an electricalinterface of the internal printed circuit board via a plug, for example.An SFP transceiver is described in DE 101 14 143 A1 for example.

EP-A-0 463 214 describes a transmission and reception module for abidirectional optical signal transmission, which is known as BIDImodule. In the case of this module the two active components, namelylight transmitter and light receiver, are incorporated as independentcomponents in a manner hermetically tightly encapsulated in a commonmodule housing, in the interior of which a beam splitter and a lenscoupling optical system are arranged. The module housing has a fiberconnection for a common optical fiber. One optical signal is coupledinto the coupled optical fiber by the transmitter, while at the sametime another optical signal can be received from the same fiber. The twosignals are separated by a beam splitter, which may also contain awavelength-selective filter which reflects a specific wavelength andallows another wavelength to pass.

WO 02/095470 A1 discloses an electro-optical module for the transmissionand/or reception of optical signals of at least two optical datachannels, in which at least two optical waveguide sections having ineach case at least one beveled end face are provided. The opticalwaveguide sections are positioned axially one behind the other at thebeveled end faces. For a specific optical channel, light is coupled inand light is coupled out at the beveled end face of an optical waveguidesection at an angle to the optical axis of the optical waveguide. Inthis case, the end face is coated with a wavelength-selective filter forwavelength separation purposes.

WO 02/084 358 discloses a transmission module for an optical signaltransmission, in which a transmission device is arranged on atransmission device substrate and a detection device is arranged on adetection device substrate and the transmission device substrate and thedetection device substrate are arranged one above the other with respectto the direction of the emitted or received light. In this case, thetransmission device substrate and/or the detection device substrate aretransparent to the wavelength emitted by the transmission device. Theknown transmission module provides an advantageous construction althoughwith only one detection device.

It is endeavored to provide transceivers of small design for abidirectional optical data transmission which can realize a high datarate and at the same time can be produced cost-effectively.

SUMMARY OF THE INVENTION

The solution according to the invention is distinguished by the conceptof arranging two bidirectional optical subassemblies in a housing ofsmall design having a width of at most 13.5 nm, both of whichsubassemblies are suitable for the simultaneous emission and receptionof optical signals. Each subassembly can in each case be opticallycoupled to an optical waveguide via an optical interface for thecoupling of two optical waveguides.

Each optical subassembly contains both an optical transmitter and anoptical receiver. It is also referred to as BOSA (bidirectional opticalsubassembly). Consequently, unlike in known transceivers, in the case ofthe present invention each subassembly is designed as a bidirectionaltransmission and reception module. Optical signals can thus betransmitted in both directions simultaneously in an optical link betweentwo transceivers on an optical waveguide, each transmission directionoperating with a different wavelength. This makes it possible toincrease the transmission capacity of an optical link and thus thecapacity of existing fiber-optic networks. At the same time, opticalsubassemblies of small design are used so that they can be integratedinto a housing of small design, in particular in accordance with the SSFor SSP industry standard.

In a preferred refinement of the invention, the transceiver additionallyhas a multiplexer and a demultiplexer. These are preferablyconcomitantly integrated into the transceiver housing, but may, inprinciple, also be arranged separately. The demultiplexer divides anelectrical data stream having a predetermined bandwidth, which is to betransmitted by the transceiver, into a first and a second partial datastream to be transmitted, in each case having a smaller bandwidth. Thefirst partial datastream to be transmitted is fed to the firstsubassembly and the second partial datastream to be transmitted is fedto the second subassembly. The first and second partial datastreams tobe transmitted are then emitted as optical signals via the first andsecond subassemblies. At the same time as the emission of opticalsignals, the first subassembly and the second subassembly receive afirst optical partial datastream to be received and a second opticalpartial datastream to be received, in each case having a specificbandwidth, convert them into electrical signals and feed the electricalsignals to the multiplexer, which combines the two received partialdatastreams into a received electrical datastream having apredetermined, higher bandwidth. In this case, preferably, thedemultiplexer is a 1:2 demultiplexer and the multiplexer is a 2:1multiplexer, the predetermined bandwidths of the data signal to betransmitted and of the received data signal being identical.

The use of a multiplexer and of a demultiplexer in the manner describedmakes it possible for the transmission capacity of the transceiver to bedoubled overall for the same data rate of the individual subassemblies.In this case, the two subassemblies are simultaneously operatedbidirectionally. Consequently, on one fiber it is possible to transportprecisely as much data as on two fibers in previous transceivers. Thecapacity of existing fiber networks can accordingly be doubled. In thiscase, it is advantageous that the increase in the transmission capacitydoes not necessitate changing the external circuitry and the electricalinterface of the transceiver. These can be maintained. Moreover, in thesubassemblies it is possible to have recourse to in each casecost-effectively available components such as vertically emitting laserdiodes (VCSEL), edge emitting lasers and pin diodes.

In a preferred embodiment of the invention, the first subassembly hasthe following components: a transmission component, which emits lighthaving a first wavelength, a reception component, which detects lighthaving a second wavelength, a carrier substrate, which is transparent tothe light having the first wavelength and on which the transmissioncomponent is arranged. A monitor component which detects a fraction ofthe light emitted by the transmission component, the reception componentbeing integrated into the carrier substrate, the reception component andthe transmission component being arranged one behind the other withrespect to the direction of the emitted or received light, the receptioncomponent being optically transparent to the light having the firstwavelength, and light emitted by the transmission component radiatingthrough the carrier substrate and the reception component.

In a preferred embodiment of the invention, the second subassembly hasthe following components: a transmission component, which emits lighthaving a second wavelength, a reception component, which detects lighthaving a first wavelength, a carrier substrate, which is transparent tothe light having the first wavelength and having the second wavelengthand on which the transmission component is arranged, and a monitorcomponent, which detects a fraction of the light emitted by thetransmission component, the reception component and the transmissioncomponent being arranged one behind the other with respect to thedirection of the emitted or received light, the transmission componentbeing optically transparent to the light having the first wavelength,light emitted by the transmission component radiating through thecarrier substrate and the light received by the reception componentradiating through the carrier substrate and the transmission components.

The two subassemblies are suitable for simultaneously transmitting datain both directions among one another via an optical link, the lightemitted by one subassembly in each case being received by the othersubassembly.

In this case, for both subassemblies, use is made of an arrangement inwhich the transmission component and reception component are arrangedone behind the other with respect to the direction of the emitted orreceived light, with the result that beam deflection is not necessary.This considerably simplifies the construction. Furthermore, a filter forwavelength separation is not absolutely necessary. In this case, use ismade of the fact that the materials used for the carrier substrate, thetransmission component and the reception component are transparent tospecific wavelengths, but in contrast are not transparent to otherwavelengths. In particular, this refinement exploits the effect thatlonger-wave light for example having a wavelength of 1310 nm can radiatethrough substrates which generate shorter-wave light of 850 nm, forexample.

A compact construction of a bidirectional subassembly with a reducednumber of parts and thus low production costs is made available in eachcase, the subassembly simultaneously permitting monitoring of the lightof the transmission component. The bidirectional subassembly constructedin this way can furthermore be embodied in a small structuralconfiguration and can be integrated into a transceiver housing of smalldesign.

The wavelengths of the transmission component and of the receptioncomponent are preferably chosen such that they correspond to thecustomary wavelengths in optical transmission technology, thus inparticular to the optical “windows” of customary optical fibers.Wavelength combinations of 850 nm/1310 nm, 850 nm/1490 nm or 850 nm/1550nm are preferable chosen for the first and second wavelengths. Acombination for the first and second wavelengths of 1310 nm/1550 nm islikewise possible.

However, the transceiver according to the invention can also be embodiedin combination with optical subassemblies that are embodied differently.In another exemplary embodiment, a subassembly has: a transmissionmicromodule, which has a laser component on a first carrier element,said laser component emitting light having a first wavelength, areception micromodule, which has a photodiode on a second carrierelement, said photodiode detecting light having a second wavelength, anda TO housing having a baseplate, which serves for the arrangement of thetransmission micromodule and of the reception micromodule, thetransmission micromodule and the reception micromodule being arrangedone above the other with respect to the emitted light or light to bedetected, and the first carrier element of the transmission micromodulebeing transparent to the light to be detected. In a preferred embodimentvariant, the baseplate of the TO housing in this case has a cutout,which serves to accommodate the reception micromodule, the transmissionmicromodule being arranged thereabove on the baseplate.

The other subassembly of the transceiver is designed identically exceptfor the fact that the respective other wavelength is emitted anddetected.

This embodiment of the subassemblies has recourse to cost-effectiveconstructional forms using a TO housing. Edge emitting laser diodes maybe used in this case. The subassembly is once again embodied in a smallstructural configuration and can be integrated into a transceiverhousing of small design.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below using a plurality ofexemplary embodiments with reference to the figures, in which:

FIG. 1 shows a diagrammatic illustration of the construction of twomutually complementary optical subassemblies for the bidirectional datatransmission.

FIG. 2 shows the construction of a first subassembly for a bidirectionaldata transmission, which emits light having a first wavelength andreceives light having a second wavelength.

FIG. 3 shows the construction of a second subassembly for abidirectional data transmission, which emits light having the secondwavelength and receives light having the first wavelength.

FIG. 4 shows a section through a housing with a subassembly inaccordance with FIG. 2 or 3.

FIG. 5 shows a perspective view of the subassembly of FIG. 4, which isconnected to a plug receptacle and is contact-connected via a flexiblefoil.

FIG. 6 shows a perspective illustration of an optoelectronic transceiverwith a housing and two subassemblies in accordance with FIG. 5 or inaccordance with FIG. 8A.

FIG. 7 shows an alternative configuration of the subassembly of FIG. 3.

FIG. 8A shows an exploded illustration of the construction of a furtherexemplary embodiment of a subassembly for a transceiver in accordancewith FIG. 6.

FIG. 8B shows a detail view of the subassembly of FIG. 8A, whichillustrates the arrangement of a micro-transmission module and of amicro-reception module on the baseplate of a TO housing.

FIG. 9 shows a block diagram of the functional components of thetransceiver of FIG. 6.

DESCRIPTION OF A PLURALITY OF PREFERRED EXEMPLARY EMBODIMENTS

FIG. 6 shows an optoelectronic transceiver 200 of small design inaccordance with the SFP industry standard. The transceiver 200 has anelongate housing 201 having a width of less than 13.5 mm. Thetransceiver 200 contains two bidirectional optical subassemblies (BOSAs)100 arranged next to one another in the housing 201, one of saidsubassemblies being illustrated. An optical interface is provided by aplug region 205 with two optical ports 203, 204. An optical waveguidecan be plugged into each optical port 203, 204, an optical couplingbetween the optical waveguide and the respective subassembly 100 beingeffected, so that each subassembly 100 can emit and receive opticalsignals via a connected optical waveguide.

The two subassemblies 100 are electrically connected to an internalprinted circuit board 202 of the transceiver 200 via a flexibleconductor, said printed-circuit board having electrical components suchas a driver module, for instance, in a customary manner. The printedcircuit board 202 can be connected to a main circuit board via anelectrical interface (not illustrated). In this case it is conceivablethat the internal printed circuit board 202 of the transceiver isdispensed with and the corresponding electrical components areadditionally integrated into the subassemblies 100.

It is pointed out that both subassemblies 100 are designed asbidirectional modules, that is to say the transceiver 200 cansimultaneously emit light having one wavelength and receive light havinganother wavelength at each port. The subassemblies 100 are embodied in asmall structural configuration, so that they fit next to one anotherinto the available housing width of 13.5 m, it generally beingnecessary, in addition, to comply with a minimum distance between thesubassemblies 100. Exemplary embodiments of the configuration of thesubassemblies 100 in a small structural configuration are describedbelow in FIGS. 1 to 5, on the one hand, and in FIGS. 8A, 8B, on theother hand.

Before these configurations of the subassemblies 100 are explained,however, firstly the functional components of the transceiver 200 willbe considered in greater detail with reference to FIG. 9.

Two bidirectional optical subassemblies 100 a, 100 b are present, whichare identical apart from the fact that the emitted and receivedwavelength are interchanged. Each subassembly 100 a, 100 b has a laserdriver 411, 421, a power monitoring device 412, 422 with an assignedautomatic shutdown unit 413, 423, a laser diode 414, 424, a monitordiode 415, 425, a beam splitter 416, 426, a photodetector 417, 427 and areception circuit 418, 428. Coupled to the beam splitter 416, 426 is anoptical waveguide 419, 429, which is preferably a single-mode opticalfiber.

The method of operation is known per se. The laser diode 414, 424 isdriven by the laser driver 411, 421, to which a digital signal to betransmitted is applied at its inputs TD−, TD+. A part of the radiationemitted by the laser diode 414, 424 is detected by the monitor diode415, 425 and fed to the power monitoring device 412, 422, which outputsa control signal to the laser driver 411, 421 in accordance with thelaser power determined. In the event of predetermined criteria beingviolated or given the presence of a corresponding external controlsignal Tx dis (Transmit disable), the laser 414, 424 is automaticallyshut down by the shutdown unit 413, 423.

The light emitted by the laser 414, 424 is coupled into the opticalfiber 419, 429 via the beam splitter 416, 426. Light is transmittedbidirectionally on the optical fiber 419, 429. Light having a wavelengthto be detected, which differs from the wavelength of the emitted lightof the laser 414, 424, is received via the optical fiber 419, 429 andfed from the beam splitter 416, 426 to the photodetector 417, 427. Thedetected signal is conditioned in the reception circuit 418, 428 andoutput as a regenerated electrical signal at outputs RD−, RD+. Theoutput “SD” (Signal Detect) indicates whether a received signal ispresent.

An external control signal Tx dis (Transmit disable) can be fedsimultaneously to both subassemblies 100 a, 100 b via a unit 430, sothat both lasers are shut down simultaneously, as necessary.

The arrangement of FIG. 9 is distinguished by the fact that, in abidirectional transceiver, the two subassemblies 100 a, 100 b areembodied as bidirectional units both with a laser 414, 424 and with adetector 417, 427. The transceiver with the subassemblies 100 a, 100 bcan communicate with a structurally identical transceiver (at the otherend of the optical fibers 419, 429). For this purpose, it is provided,for example, that the laser 414 of the subassembly 100 a emits lighthaving a wavelength of 1300 nm, while the photodiode 417 receives lighthaving a wavelength of 850 nm. By contrast, the subassembly 100 b emitslight having a wavelength of 850 nm and receives light having awavelength of 1300 nm. The respective subassembly 100 a, 100 b canaccordingly communicate with the subassembly 100 b, 100 a opposite to itin a transceiver of structurally identical design.

In this case, the wavelength combinations can be chosen virtually asdesired. Wavelength combinations of 850 nm/1310 nm, 850 nm/1490 nm, 850nm/1550 nm or else 1310/1550 nm are preferably chosen. The fact ofwhether a signal transmission between two transceivers is effected viasingle-mode or multi-mode fibers depends, inter alia, on the wavelengthcombination chosen.

The arrangement of FIG. 9 is furthermore distinguished by an additionaldemultiplexer 440 and multiplexer 450. The demultiplexer 440 is a 1:2demultiplexer and the multiplexer 450 is a 2:1 multiplexer. Their useenables the transmission capacity per fiber pair 419, 429 to be doubledwith the external circuitry of the transceiver being unchanged (i.e.with the electrical interface of the transceiver being maintained). Inthis case, as explained, two structurally identical transceivers areused for a link, the fibers of which transceivers must not cross oneanother. The data having a predetermined bandwidth that are to betransmitted are divided into two partial datastreams by thedemultiplexer 440, said partial datastreams in each case having half thebandwidth of the bandwidth to be transmitted.

The data of the two partial datastreams are in each case transmitted viaa subassembly 100 a, 100 b and the associated optical fiber 419, 429 toa structurally identical transceiver. At the same time, partialdatastreams transmitted by such a structurally identical transceiver arereceived by the subassemblies 100 a, 100 b and fed to the multiplexer450. In the multiplexer 450, the partial data streams are combined intoa received electrical datastream having the doubled, original bandwidth.In this way, it is possible to realize a data transmission bandwidthwhich is twice as large as the bandwidth of an individual lasercomponent or reception component.

In order to increase the bandwidth of the data which can be transmittedbetween two transceivers 200, it is thus provided that the datastream tobe transmitted is divided, by means of the demultiplexer 440, into twopartial datastreams each having a bandwidth of 50% of the datastream tobe transmitted. The two partial datastreams are conducted to the twooptoelectronic subassemblies 100 a, 100 b arranged in the transceiver200 and converted into optical signals. The datastream is thus dividedbetween two transmission components and—in each case with half thebandwidth—transmitted simultaneously via two connected optical fibers toa correspondingly constructed transceiver. At the other transceiver, thetwo datastreams are recombined by means of a multiplexer, so thatoverall a data transmission with a doubled bandwidth is possible incomparison with the bandwidth respectively provided by a transmitter anda receiver. By virtue of the two fibers being utilized to capacitybidirectionally and by virtue of the datastream being multiplexed anddemultiplexed, it is possible to double the capacity of existing fibernetworks.

The construction of the subassemblies of the transceiver will now bediscussed.

FIG. 1 shows an arrangement having two modules 1, 2 for a bidirectionaldata transmission. The modules are designed complementarily with respectto one another insofar as the light having a first wavelength emitted bythe first module 1 is detected by the second module 2 and the lighthaving a second wavelength emitted by the second module 2 is detected bythe first module 1. Situated between the modules 1, 2 is a signaltransmission section L, in which the signals are generally transmittedvia optical fibers or other optical waveguides. A transmission via amultimode waveguide is preferably effected. The direct confrontation ofthe modules 1, 2 in FIG. 1 is thus to be understood to be onlydiagrammatic.

The first module 1 has a carrier substrate 11, a transmission device 12,a monitor diode 13 and a reception device 14. The transmission device 12is preferably a VCSEL laser diode with a VCSEL structure 121 formed in aprefabricated chip. The laser diode 12 is mounted upside down, that isto say with the light-emitting side downward on the carrier substrate11, so that the light-emitting region 121 directly adjoins the carriersubstrate 11.

Arranged on the rear side of the laser diode 12 is a monitor diode 13with a light-sensitive pn junction 131, said monitor diode beingcontact-connected via bonding wires 9. The monitor diode 13 detects afraction of the light emitted by the laser diode 12. It is connected toa control/regulating device (not illustrated) for regulating the outputpower of the laser diode 1.

The monitor diode 13 is likewise preferably formed as a prefabricatedchip, preferably in an InP substrate. As an alternative, however, themonitor diode may also be monolithically integrated into the laser diode12. For this case, on the side remote from the carrier substrate 11, apn junction is integrated into the laser diode 12 and contact-connectedvia bonding wires 9, for instance.

The laser diode 12 emits light having a first wavelength λ1, where λ1 ispreferably 1310 nm, or alternatively about 1490 nm or about 1550 nm. Afraction of the light is coupled out from the resonator of the laserdiode 12 in the direction of the monitor diode 13 and detected by themonitor diode 13 for monitor purposes. The substrate of the laser diode12 is in this case transparent to the emitted light having thewavelength λ1, as is the substrate of the monitor diode 13. In thiscase, the substrate of the laser diode 12 is composed for example ofGaAs, which is light-transmissive to light having wavelengths above 950nm.

The carrier substrate 11 is preferably composed of silicon. Silicon istransparent to wavelengths above about 1100 nm. However, it is alsopossible to use a different material as carrier substrate which istransparent to the emitted wavelength λ1.

The reception component 14 is integrated into the carrier substrate 11.For this purpose, the carrier substrate forms a pn junction at the sideremote from the transmission component 12. The use of silicon as carriersubstrate 11 and as material of the reception component 14 isparticularly cost-effective.

The reception component 14 detects light having a second wavelength λ2,which is less than the first wavelength λ1. The carrier substrate 11 isnot transparent to the second wavelength λ2, so that an opticalisolation is present between the transmission component 12 and thereception component 14 with regard to the received light having thewavelength λ2. By contrast, the light having the wavelength λ1 emittedby the laser diode 12 radiates through the carrier substrate 11 and alsothe reception node 14 in an undisturbed manner.

If the wavelengths 1550 nm and 1310 nm are chosen for λ1 and λ2, thecarrier substrate must be composed of a different material than silicon,since silicon is transparent to these wavelengths and, consequently, anoptical isolation is no longer present between the transmissioncomponent 12 and the reception component 14 with regard to the receivedlight having the wavelength λ2. By way of example, the carrier substrate11 for this case is composed of Inp or sapphire with germanium layers.

The complementary module 2 likewise has a carrier substrate 21, atransmission component 22, a reception component 24 and a monitor diode23.

The transmission device is preferably once again a VCSEL laser diode 22with a light-emitting region 221, which emits light having the secondwavelength λ2. The laser diode 22 is fitted upside down as chip 22 onthe substrate 21. The substrate of the laser diode 22 is preferablycomposed of GaAs, which is light-transmissive to light havingwavelengths above 950 nm.

In this configuration, the reception component 24, which is preferablyformed as a prefabricated photodiode chip (for instance made of InP)with an integrated pn junction 241, is arranged on that side of thelaser diode 22 which is remote from the carrier substrate 21. Thereception diode 24 is contact-connected via bonding wires 9. Thereception diode detects light having the wavelengths λ1. In thisrespect, the module 2 is complementary to the other module 1.

The monitor diode 23 is integrated into the carrier substrate 21 in thecase of the module 2. In accordance with FIG. 1, the monitor diode 23 isin this case preferably situated on that side of the carrier substrate21 which faces the laser diode 22.

The carrier substrate 21 is transparent to the light having thewavelength λ2 emitted by the laser diode 22, as well as to the lighthaving the wavelength λ1 emitted by the laser diode 12 of thecomplementary module 1. The substrate of the laser diode 22 itself, bycontrast, is only transparent to the light having the wavelength λ1detected by the reception diode 24, and not, by contrast, to the emittedlight. Light emitted from the resonator of the laser diode 22 in thedirection of the reception diode 24 is therefore absorbed and does notdisturb the reception diode 24. The substrate of the laser diode 22accordingly acts as a blocking filter. It is optionally possible for ablocking filter additionally to be arranged on that side of the laserdiode 22 which faces the reception diode 24. Additional blocking filtersmay also be provided at the module 1.

The light having the wavelength λ2 emitted by the laser diode 22 firstlyradiates through the monitor diode 23. In this case, a small fraction ofthe emitted light is detected for monitor purposes. The non-detectedproportion radiates through the carrier substrate 21 and is coupled outfrom the module 2.

FIG. 2 shows the construction of the module 1 of FIG. 1 in somewhatgreater detail.

The VCSEL laser diode 12 is arranged by flip-chip mounting on the onetop side 115 of the silicon carrier substrate 11, which is opticallytransparent only to light having the emitted wavelengths λ1. In thiscase, the p-type contact and the n-type contact of the laser diode arearranged on the mounting side, i.e. the side facing the carriersubstrate 201. The contact-connection is effected via correspondingmetalizations on the top side 115 of the carrier substrate 11 (notillustrated).

The monitor diode 13 is mounted on the laser diode 12 on the rear sideand detects a fraction X of the light of the laser diode 12. The monitordiode 13 is electrically connected via two bonding wires 9 connected tocorresponding bonding pads on the top side of the carrier substrate (notillustrated).

Situated in the silicon carrier substrate 11 are two plated-throughholes 111, 112, which contact-connect the reception diode 14 integratedinto the carrier substrate 11. Thus, all the electrical contacts aresituated on a plane, the mounting plane, formed by the one top side 115of the carrier substrate 11. In this way, from the mounting plane 115,it is then possible to effect bonding onto a lead frame in a simplemanner, as is also illustrated in FIG. 4.

The second module 2 of FIG. 1 is illustrated in detail in FIG. 3. Thecarrier substrate 21 is transparent both to light having the detectedwavelength λ1 and to light having the emitted wavelength λ2. It ispreferably composed of sapphire. Sapphire is transparent to wavelengthsbetween 850 nm and 1550 nm.

The VCSEL laser diode 22 is once again mounted on the one side 215 ofthe carrier substrate 21 by means of flip-chip mounting, so that bothcontacts are on the same side. In this respect, the construction iscomparable to that of the laser diode 12 of FIG. 2.

The reception diode 24 with the pn junction 241, which diode is notsensitive to wavelength λ2, is mounted on the VCSEL laser diode 22 onthe rear side. A reception diode comprising an InP substrate ispreferably involved. It serves to detect the light having the wavelengthλ1 emitted by the module 1, which light has been emitted by thecomplementary module 1.

The monitor diode 23 is integrated into the sapphire. For this purpose,a crystalline silicon layer is preferably integrated into the sapphire,which layer provides a pn junction. The monitor diode 23 is preferablyformed on that side of the carrier substrate 21 which faces the laserdiode 22. This enables simple contact connection of the monitor diodevia contacts on the surface 215 of the carrier substrate.

FIG. 7 shows an alternative configuration of the module to FIG. 3. Inthe case of this configuration, the monitor diode 23′ is not integratedinto the carrier substrate 21, but is instead integrated into the laserdiode 22′ itself. For this purpose, a pn junction is integrated betweenthe VCSEL structure 221′ and the substrate (preferably composed of GaAs)of the laser diode. In this exemplary embodiment, the laser diode 22′ ismade somewhat larger than the reception diode 24, so that there is thepossibility of contact connection of a common contact of the laser diode22′ and of the integrated monitor diode 23′ via a bonding wire 9 whichis contact-connected to the carrier substrate 21 or, as an alternative,directly to a lead frame.

In this configuration, too, the substrate of the laser diode 22′ acts asa blocking filter for light emitted in the direction of the receptiondiode 24 after said light has passed through the monitor diode 23′.

FIG. 4 shows the bidirectional module 1 of FIG. 2 as a housed module 10in a standard housing. In this case, the carrier substrate 11 may have alens 6, which is situated on the optical axis and sheds the emitted orreceived light for the purpose of better coupling to an opticalwaveguide. The carrier substrate 11 is arranged on a lead frame 3, whichhas a central cutout 5 for an optical access to the module and providesthe contact connection of the module 1. Except for the optical access 5,the arrangement of module 1 and lead frame 3 is encapsulated byinjection-molding with a nontransparent plastics composition. Suchhousings are known per se, for instance from DE 102 01 102 A1, so thatthey are not discussed in any greater detail. In addition, although FIG.4 shows bidirectional module 1 and its carrier substrate 11 in housedmodule 10, a similar housed module may house bidirectional module 2 ofFIG. 3 (or bidirectional 2′ of FIG. 7) and its carrier substrate 21.

FIG. 5 shows a subassembly 100 c with the housed module 10 of FIG. 4 inconnection with an optical plug receptacle 8 for receiving an opticalwaveguide. At the same time, provision is made of a flexible conductor 7with conductor tracks and contact pads for the contact connection of theconnecting contacts of the module 10. That end of the flexible conductor7 which is not connected to the module 10 is connected to a printedcircuit board (not illustrated).

FIGS. 8A and 8B show an alternative configuration of a subassembly 100d, which can be used in an optoelectronic transceiver 200 in accordancewith FIG. 6. In this case, once again two subassemblies 100 d arearranged in an arrangement next to one another in the transceiver 200,in each case in an orientation such that the optical access of thesubassembly 100 d in each case runs parallel to the longitudinal axis ofthe transceiver 200, so that an optical coupling to an optical fiber ineach case can be effected via the optical ports 203, 204.

The subassembly 100 d has a TO housing comprising, in a manner known perse, a baseplate 310 with plated-through holes for a plurality of contactpins 320 and a cap 330 with an optical window 331, which cap is fixed inhermetically sealed fashion on the baseplate 310. The cap 330 issurrounded by a wall sleeve 340, at whose end side 341 is fitted acovering cap 350 with a coupling device 360 for receiving an opticalwaveguide to be connected, which is preferably a single-mode opticalwaveguide. In this case, in the context of an active adjustment, thecovering cap 350 is adjusted prior to final fixing with respect to thewall sleeve 340. Such a construction is known for example from WO98/10319 A1.

A transmission micromodule 370 and a reception micromodule 380 arearranged on the baseplate 310 of the TO housing. The transmissionmicromodule 370 has, as essential components, an edge emittingsemiconductor laser 371, a 45° prism 372 with a monitor diode 373, abeam splitter 374 with a beam-splitting area 375 provided with awavelength-selective filter, and a silicon carrier 376 with anintegrated lens 377. These components are arranged on a carrier 378. Thereception micromodule 380 has a photodiode 382 on a carrier 381.

A depression 311 is formed in the baseplate 310 of the TO housing, thetransmission micromodule 380 being inserted into said depression. Thetransmission micromodule 370 is arranged thereabove on the surface ofthe baseplate 310. In this case, the carrier element 378 of thetransmission micromodule is transparent to the wavelength detected bythe photodiode 382. Light emitted by the semiconductor laser 371 isreflected at the beam-splitting area 375 and radiated via the lens 377.By contrast, received light having a different wavelength passes throughthe wavelength-selective filter of the beam-splitting area 375,traverses the carrier element 387 and is detected by the photodiode 382of the reception micromodule 380. The transmission micromodule 370 andthe reception micromodule 380 are in each case contact-connected via thecontact pins 320 and bonding wires (not illustrated).

The construction described likewise provides, in a very compact manner,a subassembly with a transmission and reception arrangement by means ofwhich, simultaneously, light having a first wavelength can be emittedand light having a second wavelength can be detected.

The TO housing used preferably has external dimensions perpendicular tothe optical axis of the emerging laser light of at most 6.5 mm, therebyenabling mounting in Small Form Factor (SFF) transceivers and Small FormFactor Pluggable (SFP transceivers) of small design.

The configuration of the invention is not restricted to the exemplaryembodiments presented above, which are to be understood merely by way ofexample. The person skilled in the art recognizes that numerousalternative embodiment variants exist which, despite their deviationfrom the exemplary embodiments described, make use of the teachingdefined in the claims hereinafter.

1. An optoelectronic transceiver for a bidirectional optical signaltransmission, the optoelectronic transceiver comprising: a housinghaving a width of at most 13.5 mm; a first bidirectional opticalsubassembly arranged in the housing and serving for the simultaneousemission and reception of optical signals; a second bidirectionaloptical subassembly arranged in the housing and serving for thesimultaneous emission and reception of optical signals; and an opticalinterface for coupling two optical waveguides, such that each opticalwaveguide is optically coupled to a corresponding one of the first andsecond bidirectional optical subassemblies, wherein the firstsubassembly comprises: a transmission component for emitting lighthaving a first wavelength; and a reception component for detecting lighthaving a second wavelength, wherein at least a portion of one of thetransmission and reception components is optically transparent to thelight emitted or detected by the other of the transmission and receptioncomponents.
 2. The transceiver as claimed in claim 1, further comprisinga multiplexer and a demultiplexer, wherein the demultiplexer includesmeans for dividing an electrical data stream having a firstpredetermined bandwidth, which is to be transmitted by the transceiver,into a first and a second electrical partial data stream each having asmaller bandwidth than the first predetermined bandwidth, wherein thefirst electrical partial datastream to be transmitted is fed to thefirst subassembly and the second electrical partial datastream to betransmitted is fed to the second subassembly such that the electricalpartial datastreams are emitted simultaneously as optical signals, andwherein the first subassembly and the second subassembly are configuredto receive a first optical partial datastream and a second opticalpartial datastream, respectively, convert the respective optical partialdatastreams into electrical signals, and feed the respective opticalpartial datastreams to the multiplexer, which includes means forcombining the two received partial datastreams into a receivedelectrical datastream having a second predetermined bandwidth higherthan a bandwidth of either of the first and second optical partialdatastreams.
 3. The transceiver as claimed in claim 2, wherein thedemultiplexer comprises a 1:2 demultiplexer and the multiplexercomprises a 2:1 multiplexer, and wherein the first and secondpredetermined bandwidths are identical.
 4. The transceiver as claimed inclaim 1, wherein the multiplexer and the demultiplexer are integratedinto the transceiver.
 5. The transceiver as claimed in claim 1, whereinthe first subassembly further comprises: a carrier substrate, which istransparent to the light having the first wavelength and on which thetransmission component is arranged; and a monitor component fordetecting a fraction of the light emitted by the transmission component,wherein the reception component is integrated into the carriersubstrate, wherein the reception component and the transmissioncomponent are arranged one behind the other with respect to thedirection of the emitted or received light, wherein the receptioncomponent is optically transparent to the light having the firstwavelength, and wherein light emitted by the transmission componentradiates through the carrier substrate and the reception component. 6.The transceiver as claimed in claim 5, wherein the transmissioncomponent is mounted with its top side downward on the carriersubstrate.
 7. The transceiver as claimed in claim 5, wherein thereception component is integrated into the carrier substrate on a sideof the carrier substrate which is remote from the transmissioncomponent.
 8. The transceiver as claimed in claim 7, wherein the carriersubstrate has two plated-through holes, which issue from the side of thecarrier substrate facing the transmission component and contact-connectthe reception component.
 9. The transceiver as claimed in claim 5,wherein the reception component integrated into the carrier substrateforms a pn junction integrated into the carrier substrate.
 10. Thetransceiver as claimed in claim 5, wherein the carrier substrate is nottransparent to light having the second wavelength.
 11. The transceiveras claimed in claim 5, wherein the first wavelength is greater than thesecond wavelength.
 12. The transceiver as claimed in claim 11, whereinthe first wavelength is one of 1310 nm, 1490 nm and 1550 nm, and thesecond wavelength is one of 850 nm and 1310 nm.
 13. The transceiver asclaimed in claim 5, wherein the carrier substrate comprises silicon. 14.The transceiver as claimed in claim 5, wherein the monitor component isarranged on that side of the transmission component which is remote fromthe carrier substrate.
 15. The transceiver as claimed in claim 5,wherein the transmission component comprises a laser chip and themonitor component comprises a monitor diode chip.
 16. The transceiver asclaimed in claim 5, wherein the monitor component is integrated into thetransmission component on that side of the latter which is remote fromthe carrier substrate.
 17. The transceiver as claimed in claim 1,wherein the second subassembly comprises: a transmission component foremitting light having the second wavelength; a reception component fordetecting light having the first wavelength; a carrier substrate, whichis transparent to the light having either of the first wavelength andthe second wavelength and on which the transmission component isarranged; and a monitor component for detecting a fraction of the lightemitted by the transmission component, wherein the reception componentand the transmission component are arranged one behind the other withrespect to the direction of the emitted or received light, wherein thetransmission component is optically transparent to the light having thefirst wavelength, wherein light emitted by the transmission componentradiates through the carrier substrate, and wherein the light receivedby the reception component radiates through the carrier substrate andthe transmission components.
 18. The transceiver as claimed in claim 17,wherein the monitor component is integrated into the carrier substrate.19. The transceiver as claimed in claim 18, wherein the monitorcomponent is integrated into the carrier substrate on a side of thelatter which faces the transmission component.
 20. The transceiver asclaimed in claim 18, wherein the monitor component integrated into thecarrier substrate forms a pn junction integrated into the carriersubstrate.
 21. The transceiver as claimed in claim 17, wherein themonitor component is integrated into the transmission component.
 22. Thetransceiver as claimed in claim 17, wherein the transmission componentis arranged with its top side downward on the carrier substrate.
 23. Thetransceiver as claimed in claim 17, wherein the photosensitive layer ofthe reception component is arranged on that side of the receptioncomponent which is remote from the transmission component.
 24. Thetransceiver as claimed in claim 17, wherein the substrate of thetransmission component is not transparent to the emitted light havingthe second wavelength.
 25. The transceiver as claimed in claim 17,wherein the first wavelength is greater than the second wavelength. 26.The transceiver as claimed in claim 25, wherein the first wavelength isone of 1310 nm, 1490 nm and 1550 nm, and the second wavelength is one of850 nm and 1310 nm.
 27. The transceiver as claimed in claim 17, whereinthe carrier substrate comprises sapphire.
 28. The transceiver as claimedin claim 17, wherein the transmission component comprises a laser chipand the reception component comprises a photodiode chip.
 29. Thetransceiver as claimed in claim 17, wherein the transmission componentcomprises a vertically emitting laser diode.
 30. The transceiver asclaimed in claim 1, wherein each subassembly further comprises: a TOhousing having a baseplate, which serves for the arrangement of thetransmission component and of the reception component, wherein thetransmission component and the reception component are arranged oneabove the other with respect to one of the emitted light and the lightto be detected, and wherein the transmission component includes a lasercomponent on a first carrier element and wherein the first carrierelement is transparent to the light to be detected.
 31. The transceiveras claimed in claim 30, wherein the baseplate of the TO housing includesa cutout, which serves to accommodate the reception component, thetransmission component being arranged thereabove on the baseplate. 32.An optoelectronic transceiver for a bidirectional optical signaltransmission, the optoelectronic transceiver comprising: a firstbidirectional optical subassembly including a first emitting componentfor emitting light having a first wavelength and a first receivingcomponent for receiving light having a second wavelength; a secondbidirectional optical subassembly including a second emitting componentfor emitting light having the second wavelength and a second receivingcomponent for receiving light having the first wavelength; means forseparating a transmission signal into first and second signalcomponents; and means for simultaneously driving the first and secondemitting components such that the first emitting component generates afirst light signal in accordance with the first signal component, andthe second emitting component generates a second light signal inaccordance with the second signal component, wherein at least a portionof one of the first emitting and the first receiving components isoptically transparent to the light emitted or detected by the other ofthe first emitting and the first receiving components, and wherein atleast a portion of one of the second emitting and the second receivingcomponents is optically transparent to the light emitted or detected bythe other of the second emitting and the second receiving components.33. The optoelectronic transceiver according to claim 32, wherein saidmeans for separating comprises a demultiplexer having an input terminalcoupled to receive the transmission signal, and a pair of outputterminals respectively coupled to the first and second emittingcomponents.
 34. The optoelectronic transceiver according to claim 32,further comprising means for generating a reception signal by combininga first reception signal component and a second reception signalcomponent that are simultaneously generated by the first receivingcomponent and the second receiving component, respectively, in responseto a third light signal applied to the first receiving component and afourth light signal applied to the second receiving component,respectively.
 35. The optoelectronic transceiver according to claim 34,wherein said means for generating comprises a multiplexer having a firstinput terminal coupled to receive the first reception signal componentfrom the first receiving component, and a second input terminal coupledto receive the second reception signal component from the secondreceiving component.
 36. An optoelectronic transceiver for abidirectional optical signal transmission, the optoelectronictransceiver comprising: a first bidirectional optical subassemblyincluding a first emitting component for emitting light having a firstwavelength and a first receiving component for receiving light having asecond wavelength; a second bidirectional optical subassembly includinga second emitting component for emitting light having the secondwavelength and a second receiving component for receiving light havingthe first wavelength; and means for generating a reception signal bycombining a first reception signal component and a second receptionsignal component that are simultaneously generated by the firstreceiving component and the second receiving component, respectively, inresponse to a third light signal applied to the first receivingcomponent and a fourth light signal applied to the second receivingcomponent, respectively, wherein at least a portion of one of the firstemitting and the first receiving components is optically transparent tothe light emitted or detected by the other of the first emitting and thefirst receiving components, and wherein at least a portion of one of thesecond emitting and the second receiving components is opticallytransparent to the light emitted or detected by the other of the secondemitting and the second receiving components.
 37. The optoelectronictransceiver according to claim 36, wherein said means for generatingcomprises a multiplexer having a first input terminal coupled to receivethe first reception signal component from the first receiving component,and a second input terminal coupled to receive the second receptionsignal component from the second receiving component.